1. Field of the Invention
The present invention relates to a fixing liquid, a toner fixing method, a toner fixing apparatus, an image forming method, and an image forming apparatus.
2. Description of the Related Art
An image forming apparatus such as a printer, a facsimile machine, and a copying machine is an apparatus for forming an image, which may include a character or a symbol, on a recording medium such as a paper, a cloth, and an OHP sheet based on information of the image. Particularly, an electrophotographic image forming apparatus has been widely used in an office since a high-definition image can be formed on a normal paper with a high speed. In such an electrophotographic image forming apparatus, a heat fixing method has been widely used in which toner is fixed on a recording medium by heating or fusing the toner on the recording medium and pressurizing the fused toner. This heat-fixing method has been preferably used since a high fixing speed, a high fixed image quality, etc., can be provided.
However, approximately half or more of electric power consumed in such an electrophotographic image forming apparatus are consumed for heating toner in the heat fixing method. On the other hand, a fixing apparatus with low electric power consumption (intended for energy conservation) is desired from the viewpoint of recent measures against environmental problems. That is, a fixing method is desired which does not requires to extremely lower temperature at which toner is heated compared to the conventional one or to heat toner, for fixing the toner. Particularly, a no-heat fixing method of fixing toner on a recording medium in which toner is not heated at all is ideal in regard to low electric power consumption.
For such a no-heat fixing method, for example, Japanese Patent No. 3290513 discloses a method for wet-fixing toner which includes spraying or dropping an oil-drop-in-water-type fixing agent onto a surface of an object to be subjected to fixation on which unfixed toner is disposed at a predetermined position, so as to dissolve or swell the toner, in which agent an organic compound is dispersed and mixed in water which compound can dissolve or swell the toner and cannot be dissolved or can be hardly dissolved in water, and subsequently drying the object subjected to fixation.
However, in the wet-fixing method disclosed in Japanese Patent No. 3290513, when a large quantity of the fixing agent is provided to unfixed toner, a recording medium (an object to be subjected to fixation) such as a transcription paper absorbs a water content of the fixing agent and a wrinkle or curl is formed on the recording medium, since the oil-drop-in-water-type fixing agent is used in which agent an organic compound is dispersed and mixed in water which compound can dissolve or swell the toner and cannot be dissolved or can be hardly dissolved in water. Accordingly, stable and high speed conveyance of a recording medium which conveyance is required for an image forming apparatus is markedly interrupted. Then, where a large quantity of water contained in the fixing agent is evaporated using a dryer so as to remove the water content from the fixing agent provided on a the recording medium, an electric power is needed which corresponds to a electric power consumed in an image forming apparatus using the heat-fixing method.
Also, usually, the surface of a toner particle is water-repellently treated with hydrophobic silica, etc., in order to prevent the toner particles from absorbing the water content in atmosphere and aggregating each other and to keep the fluidity of the toner. Therefore, when an aqueous fixing liquid containing water as a dispersion medium, such as the aforementioned fixing agent, is sprayed or dropped onto unfixed toner on a recording medium, the water-repellently treated toner particles are repelled by the aqueous fixing liquid. As a result, a blank portion is formed on a toner image and a defect is produced on the image.
FIGS. 1A, 1B, and 1C are diagrams illustrating a fixing method of providing an aqueous fixing liquid to water-repellently treated toner on a recording medium. As shown in FIG. 1A, a liquid drop of an aqueous fixing liquid 13 is dropped onto a layer of water-repellently treated unfixed toner 12 transcribed on a recording paper 11 as a recording medium by a proper fixing liquid providing device. At this time, as shown in FIG. 1B, when the liquid drop of an aqueous fixing liquid 13 contacts the layer of water-repellently treated unfixed toner 12, particles of water-repellently treated unfixed toner 12 are repelled by the liquid drop of an aqueous fixing liquid 13. Consequently, as shown in FIG. 1C, the particles of water-repellently treated unfixed toner 12 which have been repelled by the liquid drop of an aqueous fixing liquid 13 are transferred to a peripheral portion of the liquid drop of an aqueous fixing liquid 13 with the diffusion of the aqueous fixing liquid 13 on and in the recording paper 11. Then, an undesired blank portion of the water-repellently treated toner is formed on the layer of water-repellently treated unfixed toner 12 transcribed on the recording paper 11 and a defect is produced on an image formed by the toner. Thus, when the aqueous fixing liquid 13 is used, there is a problem that the layer of unfixed toner 12 transcribed on the recording paper 11 is easily disturbed.
On the other hand, for a fixing liquid which does not repel water-repellently treated unfixed toner, a nonaqueous fixing liquid is disclosed in which a material capable of dissolving or swelling toner is dissolved in a nonaqueous solvent. For example, Japanese Laid-Open Patent Application No. 2004-109749 discloses a fixing liquid in which an ester from an aliphatic dibasic acid, etc., as a material component capable of dissolving or swelling a resin component constituting toner, is diluted with (or dissolved in) nonvolatile dimethyl silicone as a diluent (or solvent). Also, for a fixing solution which can be used in a fixation method that an unfixed image formed by an electrostatic method can be sharply or easily fixed on an image receiving sheet without disturbing an image, Japanese Laid-Open Patent Application No. 59-119364 discloses a solution for fixing an unfixed toner image, which can dissolve toner and is obtained by mixing 8-120 parts by volume of a silicone oil into 100 parts by volume of a solvent having a compatibility with the silicone oil on a mutual dissolution condition. Since such a nonaqueous fixing liquid contains a nonaqueous solvent having a high affinity with water-repellently treated unfixed toner, the toner can be dissolved or swelled and fixed on a recording medium without repelling the water-repellently unfixed toner.
Herein, the use of a VOC (volatile organic compound) as a nonaqueous solvent used for a nonaqueous fixing liquid has an adverse affect on a human body, causes the generation of unpleasant odor and, therefore, is not preferable. Consequently, a nonvolatile nonaqueous solvent is practically used as a nonaqueous solvent used in a nonaqueous fixing liquid.
However, a nonaqueous fixing liquid in which a material capable of dissolving or swelling toner is dissolved in a nonvolatile nonaqueous solvent has a high permeability into a recording medium. Therefore, when a nonaqueous fixing liquid as described above is sprayed or dropped onto unfixed toner on a recording medium, the nonaqueous fixing liquid has a high speed for diffusing on or in the recording medium and penetrating through the recording medium and only a portion of the material capable of dissolving or swelling toner contained in the nonaqueous fixing liquid dissolves or swells the unfixed toner on the recording medium. Then, the residual portion of the material capable of dissolving or swelling toner is not utilized for dissolving or swelling the toner and diffuses on or in the recording medium and penetrates through the recording medium with the nonaqueous solvent. Thus, since only a portion of the material capable of dissolving or swelling toner contained in the nonaqueous fixing liquid dissolves or swells the unfixed toner on the recording medium, it is necessary to increase the concentration of the material capable of dissolving or swelling toner contained in the nonaqueous fixing liquid. For example, the inventors have found that the concentration of a solvent dissolved into a silicone oil as a nonaqueous solvent for the fixing solution disclosed in Japanese Laid-Open Patent Application No. 59-119364 is necessarily 20% by weight or greater. Therefore, in regard to a nonaqueous fixing liquid in which a material capable of dissolving or swelling toner is dissolved in a nonvolatile nonaqueous solvent, the efficiency of dissolving or swelling the toner with the material capable of dissolving or swelling toner is low.
FIGS. 2A, 2B and 2C are diagrams illustrating a fixing method in which a nonaqueous fixing liquid is provided to water-repellently treated toner on a recording medium in which liquid a material capable of dissolving or swelling toner is dissolved in a nonvolatile nonaqueous solvent. As shown in FIG. 2A, a liquid drop of a nonaqueous fixing liquid 23 in which a material capable of dissolving or swelling toner is dissolved in a nonvolatile nonaqueous solvent is dropped onto a layer of water-repellently treated unfixed toner 22 transcribed on a recording paper 21 as a recording medium by a proper fixing liquid providing device. At this time, as shown in FIG. 2B, the nonaqueous fixing liquid 23 contacting the recording paper 21 has a high permeability into the recording paper 21 and rapidly permeates into the recording paper 21. As a result, as shown in FIG. 2C, only a portion of the material capable of dissolving or swelling toner contained in the nonaqueous fixing liquid 23 can dissolve or swell the unfixed toner 22 on the recording paper 21 but the residual portion of the material capable of dissolving or swelling toner permeates and diffuses in the recording paper 21 with the nonvolatile nonaqueous solvent without dissolving or swelling the unfixed toner 22 on the recording paper 21. Thus, when a nonaqueous fixing liquid in which a material capable of dissolving or swelling toner is dissolved in a nonvolatile nonaqueous solvent is used, there is a problem that the utilization efficiency of the material capable of dissolving or swelling toner is low.
Consequently, a fixing liquid capable of fixing toner on a recording medium more efficiently has been desired.